1. Field of the Invention
The present invention relates to semiconductor packages, and more particularly, to a semiconductor package assembly that provides a true die to external fiber optic cable connection.
2. Description of the Related Art
Most computer and communication networks today rely on copper wiring to transmit data between nodes in the network. Since the data transmitted over the copper wire and the data processed within the nodes are both represented in the form of electrical signals, the transfer of data at the node-copper wire interface is straight forward. Other than perhaps a level shift and a signal amplification, no other signal processing is required for data transmitted over the copper wire to be decoded by the node. The drawback with using copper wire is its relatively low bandwidth. Copper""s ability to transmit data is significantly limited compared to other mediums, such as fiber optics. Accordingly much of the computer and communication networks being built today, including the Internet, are using fiber optic cabling instead of copper wire.
With fiber optic cabling, data is transmitted using light signals, not electrical signals. For example, a logical one may be represented by a light pulse of a specific duration and a logical zero may be represented by the absence of a light pulse for the same duration. In addition, it is also possible to transmit at the same time multiple colors of light over a single strand of optic fiber, with each color of light representing a distinct data stream. Since light is attenuated less in fiber than electrons traveling through copper, and multiple data streams can be transmitted at one time, the bandwidth of optic fiber is significantly greater than copper.
While fiber optic cabling is very efficient for transferring data, the use of light signals to process data is still very difficult. Data is typically transferred and stored in various locations before, during and after it is operated on in a computer. There still is no efficient way to xe2x80x9cstorexe2x80x9dlight signals representative of data. Networks will therefore likely continue using fiber optics for transmitting data between nodes and silicon chips to process the data within the nodes for the foreseeable future. The interface between the fiber optic cable and the nodes that process the data is therefore problematic because signals need to be converted between the electrical and the light domains.
Fiber optic transceivers, which convert light signals from a fiber optic cable into electrical signals, and vice versa, are used as the interface between a fiber optic line and a computer node. A typical transceiver includes a substrate, grooves etched in the substrate to receive the individual fiber optic strands, one or more semiconductor devices mounted on the substrate, one or more discrete optical detectors for converting light signals received over the fiber optic cables into electrical signals, one or more discrete optical transmitters for converting electrical signals from the semiconductor devices into light signals. A number of fiber optic transceivers are commercially available from Hewlett Packard, AMP, Sumitomo, and Lasermate Corporate. The problem with all of these fiber optic transceivers is that they are expensive and difficult to fabricate. With each transceiver, the semiconductor devices, transmitters, and optical detectors have to be individually mounted onto the substrate, which is a costly and time consuming process. This limits the applications in which optical interconnects versus copper. Furthermore the use of discrete transmitters and optical detectors adversely effects the performance of the transceiver because electrical parasitics between discrete components are sources of electrical attenuation of inter-chip signals at Gigabit per second speeds that are generally used with such transceivers, and power is consumed for driving these traces than would not be needed for an integrated device. The form factor of the on-board optical transceiver is relatively large and therefore does not facilitate inter-board and chip-to-chip optical interconnectability.
A low cost semiconductor device that provides a true die to external fiber optic connection is therefore needed.
The present invention provides a low cost device that provides a true die to external fiber optic connection. The device includes a semiconductor die having a first surface, an integrate circuit fabricated on the first surface of the semiconductor die and a package encapsulating the semiconductor die. At least one solder ball formed on the first surface of the die is exposed through the package encapsulating the die. The device also includes a module mounted onto the package and configured to receive an external fiber optic cable via either a direct xe2x80x9cpigtailxe2x80x9d connection or by use of an external connector. An opto-electric device, which can be either a transmitter and/or a detector, is housed in the module and is optically coupled to the fiber optic cable when the cable is inserted into the module. At least one electrical conductor is provided between the integrated circuit and the opto-electrical device. In one embodiment, the electrical conductor includes a post formed through the base of the module and which is in electrical contact between the opto-electric device and the solder ball formed on the surface of the semiconductor die, thus forming a true die to external fiber optic connection. In an alternative embodiment, the semiconductor die can have an array of the solder balls which can be used to form a plurality of true die to external fiber optic connections with additional opto-electric devices contained in the module.